Don't beat yourself up. It's the nature. It doesn't matter how "properly" you introduce your fish, if you feed your fish strictly pellets, or your fish have lived together for years, it just happened when you have predator fish in the tank. My group of Dorado has lived with the group of silver dollar for more than a year, all eat pellets. Once in a while, they decide to take a silver dollar out for target practice. It started with a small bite in the morning, and by the end of the day, all left is a small head on the bottom of the tank. It only stopped when I moved the SD out
